WO2015079920A1 - 偏光フィルムの製造方法 - Google Patents
偏光フィルムの製造方法 Download PDFInfo
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- WO2015079920A1 WO2015079920A1 PCT/JP2014/080019 JP2014080019W WO2015079920A1 WO 2015079920 A1 WO2015079920 A1 WO 2015079920A1 JP 2014080019 W JP2014080019 W JP 2014080019W WO 2015079920 A1 WO2015079920 A1 WO 2015079920A1
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- film
- water
- contact
- width direction
- pva
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B5/00—Optical elements other than lenses
- G02B5/30—Polarising elements
- G02B5/3083—Birefringent or phase retarding elements
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J7/00—Chemical treatment or coating of shaped articles made of macromolecular substances
- C08J7/02—Chemical treatment or coating of shaped articles made of macromolecular substances with solvents, e.g. swelling agents
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C55/00—Shaping by stretching, e.g. drawing through a die; Apparatus therefor
- B29C55/02—Shaping by stretching, e.g. drawing through a die; Apparatus therefor of plates or sheets
- B29C55/04—Shaping by stretching, e.g. drawing through a die; Apparatus therefor of plates or sheets uniaxial, e.g. oblique
- B29C55/06—Shaping by stretching, e.g. drawing through a die; Apparatus therefor of plates or sheets uniaxial, e.g. oblique parallel with the direction of feed
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J2329/00—Characterised by the use of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by an alcohol, ether, aldehydo, ketonic, acetal, or ketal radical; Hydrolysed polymers of esters of unsaturated alcohols with saturated carboxylic acids; Derivatives of such polymer
- C08J2329/02—Homopolymers or copolymers of unsaturated alcohols
- C08J2329/04—Polyvinyl alcohol; Partially hydrolysed homopolymers or copolymers of esters of unsaturated alcohols with saturated carboxylic acids
Definitions
- the present invention can suppress the folding of the end portion of the polyvinyl alcohol film, hardly cause the film to break during stretching or drying, and has a polarizing performance.
- the present invention relates to a method for producing a polarizing film capable of easily producing an excellent polarizing film.
- a polarizing plate having a light transmission and shielding function is a basic component of a liquid crystal display (LCD) together with a liquid crystal that changes a polarization state of light.
- LCD liquid crystal display
- Many polarizing plates have a structure in which a protective film such as a cellulose triacetate (TAC) film is bonded to the surface of a polarizing film.
- TAC cellulose triacetate
- iodine dye stretched film was oriented uniaxially stretched (I 3 - and I 5 -, etc.), such as a dichroic organic dye dichroic dye is adsorbed What you are doing is the mainstream.
- a polarizing film is usually obtained by uniaxially stretching a PVA film preliminarily containing a dichroic dye, adsorbing a dichroic dye simultaneously with uniaxial stretching of the PVA film, or uniaxially stretching the PVA film. It is continuously produced by adsorbing chromatic dyes.
- LCDs are used in a wide range of devices such as small devices such as calculators and wrist watches, notebook computers, liquid crystal monitors, liquid crystal color projectors, liquid crystal televisions, in-vehicle navigation systems, mobile phones, and measuring devices used indoors and outdoors.
- small devices such as calculators and wrist watches
- notebook computers liquid crystal monitors, liquid crystal color projectors, liquid crystal televisions, in-vehicle navigation systems, mobile phones, and measuring devices used indoors and outdoors.
- LCDs liquid crystal monitors
- liquid crystal color projectors liquid crystal televisions
- in-vehicle navigation systems mobile phones
- mobile phones and measuring devices used indoors and outdoors.
- thinner polarizing plates such as small notebook personal computers and mobile phones.
- One way to reduce the thickness of the polarizing plate is to reduce the thickness of the polarizing film.
- a thin PVA film is liable to break when stretched or dried, and the productivity and yield of the polarizing film are reduced, leading to high costs.
- Patent Document 1 and 2 As a technique for producing a thin polarizing film without causing breakage of the film, there is known a method of forming a thin PVA layer on a plastic film by a coating method and stretching the laminate (for example, Patent Document 1 and 2).
- the method using a laminate formed by forming a PVA layer on a plastic film by a coating method has the following problems.
- the present invention is a method for producing a polarizing film, which is capable of easily producing a polarizing film that is less likely to break during stretching or drying even when a thin PVA film is used, and that has excellent polarizing performance.
- the purpose is to provide.
- the inventors of the present invention when producing a polarizing film using a thin PVA film, remove the PVA film such as a swelling process and a dyeing process performed before stretching.
- PVA film with water adhering to the surface after passing through the water contact step to be contacted with the surface tends to bend at the end in the width direction, and this causes breakage in the subsequent stretching step.
- PVA film with water adhering to the surface even after stretching is still likely to be folded at the end in the width direction, which causes the film to break due to shrinkage in the subsequent drying process. It tends to occur, and a gas such as air is blown on both ends of the PVA film with water attached to the surface.
- the occurrence of folding at the end in the width direction of the PVA film is suppressed by bringing a thin body such as a film into contact, and the film breaks during stretching or drying (stretch breakage, etc.)
- the present invention was completed through further studies based on these findings.
- the present invention [1] A method for producing a polarizing film having a stretching step of stretching a PVA film, which includes a step of blowing gas and / or contacting a thin body on both ends in the width direction of the PVA film having water attached to the surface.
- [3] production method [5] The PVA film in the portion where the thin body is in contact with both ends in the width direction with respect to the length in the length direction of the PVA film between the PVA film and the first contact roll after leaving the water surface
- a manufacturing method including a step of bringing a thin body into contact with both ends in the width direction of a PVA film having water attached to the surface, wherein both ends in the width direction of the PVA film are thin at a portion where the PVA film is separated from the water surface.
- a manufacturing method including a step of bringing a thin body into contact with both end portions in the width direction of a PVA film having water attached to the surface, wherein two or more rolls sequentially contacting the PVA film having water attached to the surface.
- a production method comprising a step of bringing a thin body into contact with both ends in the width direction of a PVA film having water attached to the surface, wherein the width of the thin body is 1 cm or more.
- a manufacturing method including a step of bringing a thin body into contact with both ends in the width direction of a PVA film having water attached to the surface, wherein the water contact angle of the thin body at a portion in contact with the PVA film is 90 ° or less Any one of the production methods of [1] to [9] above; [11] The production method according to any one of [1] to [10] above, wherein a gas having a wind speed of 0.1 m / second or more is blown to both ends in the width direction of the PVA film having water attached thereto; [12] The method according to any one of [1] to [11] above, further comprising a step of bringing a plastic film into contact with both ends in the width direction of the PVA film having water attached thereto; [13] Any of the above [1] to [12], which includes a step of blowing a gas and / or contacting a thin body on both ends in the width direction of the PVA film having water attached to the surface
- the polarizing film is less likely to break during stretching or drying, and a polarizing film excellent in polarizing performance can be easily produced.
- a manufacturing method is provided.
- FIG. 4 is a schematic diagram showing the positions of L1 and L2 in a particular embodiment.
- FIG. 6 is a schematic diagram showing the positions of L3 and L4 in a particular embodiment. It is the schematic which shows the manufacturing method of the polarizing film in Example 7.
- the production method of the present invention for producing a polarizing film has a stretching step of stretching a PVA film. And in the manufacturing method of the present invention, water adheres to the surface, which is generated by passing a PVA film such as a swelling step, a dyeing step, a cross-linking step, a stretching step, a fixing treatment step, etc. through a water contact step that makes contact with water. It has the process of spraying gas and / or the process of making a thin body contact with respect to the width direction both ends of a PVA film.
- the step of blowing the gas and the step of bringing the thin body into contact with each other may be employed together, or only one of them may be employed.
- both processes may be performed on the same part of the PVA film with water adhering to the surface (for example, one side and the other side of the corresponding part of the PVA film). Both steps may be carried out in different parts of the PVA film.
- PVA film As PVA constituting the PVA film, vinyl esters such as vinyl acetate, vinyl formate, vinyl propionate, vinyl butyrate, vinyl pivalate, vinyl versatate, vinyl laurate, vinyl stearate, vinyl benzoate, isopropenyl acetate, etc. Those obtained by saponifying a polyvinyl ester obtained by polymerizing one or more of the above can be used. Among the above-mentioned vinyl esters, a compound having a vinyloxycarbonyl group (H 2 C ⁇ CH—O—CO—) in the molecule is preferable from the viewpoint of ease of production, availability, and cost of PVA, More preferred is vinyl acetate.
- the polyvinyl ester is preferably obtained using only one or two or more vinyl esters as monomers, and more preferably obtained using only one vinyl ester as a monomer.
- a copolymer of one or more vinyl esters and other monomers copolymerizable therewith may be used.
- Examples of the other monomer copolymerizable with the vinyl ester include ⁇ -olefins having 2 to 30 carbon atoms such as ethylene, propylene, 1-butene, and isobutene; (meth) acrylic acid or a salt thereof; (Meth) methyl acrylate, (meth) ethyl acrylate, (meth) acrylate n-propyl, (meth) acrylate i-propyl, (meth) acrylate n-butyl, (meth) acrylate i-butyl, ( (Meth) acrylic acid esters such as t-butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, dodecyl (meth) acrylate and octadecyl (meth) acrylate; (meth) acrylamide; N-methyl ( (Meth) acrylamide, N-ethyl (meth) acrylamide, N,
- Vinyl ether vinyl cyanide such as (meth) acrylonitrile
- vinyl halide such as vinyl chloride, vinylidene chloride, vinyl fluoride, vinylidene fluoride
- Allyl compounds such as allyl acetate and allyl chloride; maleic acid or salts thereof, esters or acid anhydrides; itaconic acid or salts thereof, esters or acid anhydrides
- vinylsilyl compounds such as vinyltrimethoxysilane; unsaturated sulfonic acids or salts thereof And so on.
- Said polyvinyl ester can have a structural unit derived from 1 type, or 2 or more types of an above described other monomer.
- the proportion of structural units derived from the other monomers in the polyvinyl ester is preferably 15 mol% or less based on the number of moles of all structural units constituting the polyvinyl ester, and is preferably 10 mol% or less. More preferably, it is more preferably 5 mol% or less.
- those not graft-copolymerized can be preferably used, but PVA can be used for one or more kinds of graft copolymer as long as the effects of the present invention are not significantly impaired. It may be modified with a monomer.
- the said graft copolymerization can be performed with respect to at least one of polyvinyl ester and PVA obtained by saponifying it.
- the graft copolymerizable monomer include unsaturated carboxylic acids or derivatives thereof; unsaturated sulfonic acids or derivatives thereof; ⁇ -olefins having 2 to 30 carbon atoms, and the like.
- the proportion of structural units derived from the graft copolymerizable monomer in the polyvinyl ester or PVA is preferably 5 mol% or less based on the number of moles of all structural units constituting the polyvinyl ester or PVA.
- the hydroxyl group may be cross-linked or may not be cross-linked.
- the PVA may have a hydroxyl group partially reacted with an aldehyde compound such as acetaldehyde or butyraldehyde to form an acetal structure, or may not react with these compounds to form an acetal structure. Also good.
- the polymerization degree of the above PVA is not particularly limited, but is preferably 1,000 or more.
- the degree of polymerization of PVA is 1,000 or more, the polarizing performance of the obtained polarizing film can be further improved. If the degree of polymerization of PVA is too high, it tends to lead to an increase in the production cost of PVA and poor processability during film formation, so the degree of polymerization of PVA should be in the range of 1,000 to 10,000. Is more preferably 1,500 to 8,000, even more preferably 2,000 to 5,000.
- the degree of polymerization of PVA as used herein means the average degree of polymerization measured according to the description of JIS K6726-1994.
- the saponification degree of PVA is preferably 99.0 mol% or more, more preferably 99.8 mol% or more, and 99.9 mol% or more because the heat and heat resistance of the obtained polarizing film is improved. More preferably.
- the saponification degree of PVA refers to the vinyl alcohol unit relative to the total number of moles of structural units (typically vinyl ester units) and vinyl alcohol units that can be converted into vinyl alcohol units by saponification of PVA. Refers to the proportion (mol%) occupied by the number of moles.
- the degree of saponification can be measured according to the description of JIS K6726-1994.
- the PVA film may contain a plasticizer together with the above PVA.
- a plasticizer polyhydric alcohol is preferably used, and specific examples include ethylene glycol, glycerin, propylene glycol, diethylene glycol, diglycerin, triethylene glycol, tetraethylene glycol, trimethylolpropane, and the like.
- PVA film Can contain one or more of these plasticizers. Among these, glycerin is preferable because the stretchability of the PVA film becomes better.
- the content of the plasticizer in the PVA film is preferably 3 to 20 parts by mass, more preferably 5 to 17 parts by mass, and still more preferably 7 to 14 parts by mass with respect to 100 parts by mass of PVA. .
- the content of the plasticizer in the PVA film is 3 parts by mass or more with respect to 100 parts by mass of PVA, the stretchability of the PVA film is improved.
- the content of the plasticizer in the PVA film is 20 parts by mass or less with respect to 100 parts by mass of PVA, the plasticizer bleeds out on the surface of the PVA film and the handling property of the PVA film is reduced. be able to.
- a PVA film is produced using a film-forming stock solution for producing a PVA film, which will be described later, the film-forming property is improved and the occurrence of film thickness unevenness is suppressed, and a metal roll is used for film-forming. Since a PVA film can be easily peeled off from these metal rolls and belts when a belt or a belt is used, it is preferable to add a surfactant to the film-forming stock solution.
- the PVA film may contain a surfactant.
- surfactant that is blended in the film-forming stock solution for producing the PVA film, and thus the surfactant contained in the PVA film, but from the viewpoint of releasability from a metal roll or belt, an anion is used.
- Surfactants or nonionic surfactants are preferred, and nonionic surfactants are particularly preferred.
- anionic surfactant for example, a carboxylic acid type such as potassium laurate; a sulfate ester type such as octyl sulfate; a sulfonic acid type such as dodecylbenzene sulfonate is suitable.
- Nonionic surfactants include, for example, alkyl ether types such as polyoxyethylene oleyl ether; alkylphenyl ether types such as polyoxyethylene octylphenyl ether; alkyl ester types such as polyoxyethylene laurate; polyoxyethylene laurylamino Alkylamine type such as ether; alkylamide type such as polyoxyethylene lauric acid amide; polypropylene glycol ether type such as polyoxyethylene polyoxypropylene ether; alkanolamide type such as lauric acid diethanolamide and oleic acid diethanolamide; polyoxy An allyl phenyl ether type such as alkylene allyl phenyl ether is preferred. These surfactants can be used alone or in combination of two or more.
- the content of the surfactant in the film-forming stock solution, and thus the content of the surfactant in the PVA film is determined as the film-forming stock solution or the PVA film.
- the amount is preferably in the range of 0.01 to 0.5 parts by mass, more preferably in the range of 0.02 to 0.3 parts by mass with respect to 100 parts by mass of PVA contained in.
- the content of the surfactant is 0.01 parts by mass or more with respect to 100 parts by mass of PVA, the film forming property and the peelability can be improved.
- the content of the surfactant is 0.5 parts by mass or less with respect to 100 parts by mass of PVA, the surfactant bleeds out on the surface of the PVA film, resulting in blocking, and handling properties are reduced. Can be suppressed.
- the PVA film may be composed only of PVA, or may be composed only of PVA and the above-described plasticizer and / or surfactant. If necessary, an antioxidant, an antifreeze agent, a pH adjuster, You may contain other components other than above-mentioned PVA, a plasticizer, and surfactant, such as a masking agent, a coloring inhibitor, and an oil agent.
- the PVA content in the PVA film is preferably in the range of 50 to 100% by mass, more preferably in the range of 80 to 100% by mass, and in the range of 85 to 100% by mass. Further preferred.
- the thickness of the PVA film is not particularly limited. However, when a thin PVA film is used, the above-described folding tends to occur at the end in the width direction, and the effect of the present invention is more effective when a thin PVA film is used.
- the thickness is preferably 50 ⁇ m or less, more preferably 45 ⁇ m or less, still more preferably 35 ⁇ m or less, particularly preferably 25 ⁇ m or less, and particularly preferably 20 ⁇ m or less because it is remarkably played. Most preferred. Although there is no restriction
- the PVA film may be a single layer or a laminate in which a PVA layer and other layers are laminated, but it is a single layer because the effects of the present invention are more remarkably exhibited. It is preferable.
- the thickness of the PVA layer is preferably in the above range.
- the shape of the PVA film is not particularly limited, but is preferably a long film because the polarizing film can be continuously produced with high productivity.
- the length of the long film is not particularly limited, and can be set as appropriate according to the application of the polarizing film to be produced.
- the length can be in the range of 5 to 20,000 m.
- variety of the said elongate film For example, although it can be 50 cm or more, since the wide polarizing film is calculated
- the width of the long film is preferably 7 m or less.
- the manufacturing method of a PVA film is not specifically limited, The manufacturing method from which the thickness and width
- above-mentioned PVA which comprises a PVA film, and as needed
- the film-forming stock solution contains at least one of a plasticizer, a surfactant, and other components, it is preferable that these components are uniformly mixed.
- liquid medium used for the preparation of the membrane forming stock solution examples include water, dimethyl sulfoxide, dimethylformamide, dimethylacetamide, N-methylpyrrolidone, ethylene glycol, glycerin, propylene glycol, diethylene glycol, triethylene glycol, and tetraethylene glycol. , Trimethylolpropane, ethylenediamine, diethylenetriamine and the like, and one or more of them can be used. Among these, water is preferable from the viewpoint of a small environmental load and recoverability.
- the volatile fraction of the film-forming stock solution (the content ratio of volatile components such as a liquid medium removed by volatilization or evaporation during film-forming in the film-forming stock solution) varies depending on the film-forming method, film-forming conditions, etc., but 50 to 95 It is preferably in the range of mass%, more preferably in the range of 55 to 90 mass%, and still more preferably in the range of 60 to 85 mass%.
- the volatile fraction of the film-forming stock solution is 50% by mass or more, the viscosity of the film-forming stock solution does not become too high, and filtration and defoaming are smoothly performed during preparation of the film-forming stock solution, and there are few foreign matters and defects. Film production is facilitated.
- the volatile fraction of the film-forming stock solution is 95% by mass or less, the concentration of the film-forming stock solution does not become too low, and the production of an industrial PVA film becomes easy.
- Examples of the film forming method for forming a PVA film using the above-described film forming stock solution include a cast film forming method, an extrusion film forming method, a wet film forming method, a gel film forming method, and the like.
- a membrane method and an extrusion film forming method are preferred. These film forming methods may be used alone or in combination of two or more.
- the extrusion film forming method is more preferable because a PVA film having a uniform thickness and width and good physical properties can be obtained.
- the PVA film can be dried or heat-treated as necessary.
- a gas is blown to the both ends in the width direction of the PVA film having water attached to the surface and / or a thin body produced by passing through a water contact step of bringing the PVA film into contact with water.
- the polarizing film can be usually produced through each process such as a swelling process, a dyeing process, a crosslinking process, a stretching process, and a fixing treatment process, and the production method of the present invention is one or two of these processes. More than one can be included as the water contact step.
- the water contact step may be either a water spraying step of spraying water on the PVA film or a water immersion step of immersing the PVA film in water, but the ease and productivity of manufacturing the polarizing film From the viewpoint of the above, it is preferable to be a water immersion step.
- the production method of the present invention is at least one selected from the group consisting of a swelling process, a dyeing process, a crosslinking process, a stretching process, and a fixing process process.
- the PVA film after taking out the PVA film immersed in water by the water immersion step is usually the above-described PVA film having water attached to the surface.
- the water used in the water contact step is not limited to pure water, and an aqueous solution or an aqueous dispersion as described later can be used according to the purpose of each step.
- the swelling process in a swelling process can be performed by immersing a PVA film in water.
- the temperature of the water when immersed in water is preferably in the range of 20 to 40 ° C., more preferably in the range of 22 to 38 ° C., and preferably in the range of 25 to 35 ° C. Further preferred.
- the time for immersion in water is, for example, preferably in the range of 0.5 to 5 minutes, and more preferably in the range of 1 to 3 minutes.
- the water at the time of immersing in water is not limited to pure water, The aqueous solution in which various components melt
- staining process can be performed by immersing a PVA film in the aqueous solution containing a dichroic dye.
- concentration of the dichroic dye in the aqueous solution containing the dichroic dye can be appropriately set according to the type of the dichroic dye to be used, for example, within the range of 0.001 to 1% by mass.
- iodine-based dye can be efficiently adsorbed on the PVA film, so that the concentration of iodine (I 2 ) used is Is preferably in the range of 0.01 to 1.0 mass%, and the concentration of potassium iodide (KI) used is preferably in the range of 0.01 to 10 mass%.
- the temperature of the aqueous solution containing the dichroic dye is preferably in the range of 20 to 50 ° C., and preferably in the range of 25 to 40 ° C., because the dichroic dye can be efficiently adsorbed to the PVA film. It is more preferable.
- staining process can be abbreviate
- dichroic dye examples include iodine based dye (I 3 - and I 5 -, etc.), and the like dichroic organic dyes.
- the iodine dye can be obtained, for example, by bringing iodine (I 2 ) into contact with potassium iodide.
- dichroic organic dye examples include direct black 17, 19, 154; direct brown 44, 106, 195, 210, 223; direct red 2, 23, 28, 31, 37, 39, 79, 81, 240, 242, 247; Direct Blue 1, 15, 22, 78, 90, 98, 151, 168, 202, 236, 249, 270; Direct Violet 9, 12, 51, 98; Direct Green 1, 85; Direct Yellow 8, 12, 44, 86, 87; Direct Orange 26, 39, 106, 107 and the like.
- dichroic dyes iodine-based dyes are preferable from the viewpoints of handleability, availability, and polarization performance.
- the dichroic dye may either be two or more even alone, for example, I 3 - may be a balanced mixture as - and I 5.
- the crosslinking step is preferably performed after the dyeing step.
- the crosslinking treatment can be performed by immersing the PVA film in an aqueous solution containing a crosslinking agent.
- a crosslinking agent one or more of boron compounds such as boric acid and borate such as borax can be used.
- the concentration of the crosslinking agent in the aqueous solution containing the crosslinking agent is preferably in the range of 1 to 15% by mass, and more preferably in the range of 2 to 7% by mass.
- the aqueous solution containing a crosslinking agent may contain an auxiliary agent such as potassium iodide.
- the temperature of the aqueous solution containing the crosslinking agent is preferably in the range of 20 to 50 ° C., and more preferably in the range of 25 to 40 ° C.
- the PVA film can be stretched during the water contact step and / or during each water contact step when the water contact step spans multiple steps.
- the draw ratio of the pre-stretching is preferably 4 times or less based on the original length of the PVA film before stretching from the viewpoint of the polarizing performance of the polarizing film to be obtained, and is in the range of 1.5 to 3.5 times More preferably, it is within.
- the stretching ratio in each water contact step for example, the stretching ratio in the swelling step is preferably in the range of 1.1 to 3 times, and in the range of 1.2 to 2.5 times.
- the draw ratio in the dyeing step is preferably 2 times or less, more preferably 1.8 times or less.
- the draw ratio in the crosslinking step is preferably 2 times or less, more preferably 1.5 times or less. More preferably, it is in the range of 0.05 to 1.3 times.
- the stretching method is not particularly limited, and may be performed by either a wet stretching method or a dry stretching method.
- the wet stretching method it can be carried out in an aqueous solution containing one or two or more of boron compounds such as boric acid such as boric acid and borax, or in an aqueous solution containing the dichroic dye described above. It can also be performed in a fixed treatment bath described later.
- the dry stretching method stretching may be performed at room temperature, stretching may be performed while applying heat, or stretching may be performed after water absorption.
- the wet stretching method is preferable from the viewpoint of the uniformity of the thickness in the width direction of the obtained polarizing film, and it is more preferable to stretch in a boric acid aqueous solution.
- concentration of boric acid in the boric acid aqueous solution is preferably within the range of 0.5 to 6.0% by mass, more preferably within the range of 1.0 to 5.0% by mass, More preferably, it is in the range of -4.0 mass%.
- the aqueous solution containing the boron compound may contain potassium iodide, and its concentration is preferably in the range of 0.01 to 10% by mass.
- the temperature at which the PVA film is stretched in the stretching step is preferably within a range of 30 to 90 ° C, more preferably within a range of 40 to 80 ° C, and within a range of 50 to 70 ° C. Is more preferable.
- the stretching ratio in the stretching step is preferably 1.2 times or more, more preferably 1.5 times or more, and more preferably 2 times or more, because a polarizing film superior in polarization performance can be obtained. Is more preferable.
- the total draw ratio including the above-described draw ratio of the pre-stretch (the ratio obtained by multiplying the draw ratios of the respective stretches) is 5.5 times or more based on the original length of the PVA film used. Is preferably 5.7 times or more, more preferably 5.8 times or more, and particularly preferably 5.9 times or more. By setting each stretching ratio within the above range, a polarizing film having better polarizing performance can be obtained.
- the upper limit of the total draw ratio is not particularly limited, but is preferably 8 times or less.
- the stretching of the PVA film in the stretching step is preferably uniaxial stretching from the viewpoint of the performance of the obtained polarizing film.
- the direction of uniaxial stretching and uniaxial stretching or lateral uniaxial stretching in the length direction of a long film can be adopted, but since it is easy to obtain a polarizing film superior in polarization performance, in the length direction Uniaxial stretching is preferred.
- Uniaxial stretching in the length direction can be performed by changing the peripheral speed between the rolls using a stretching apparatus including a plurality of rolls parallel to each other.
- lateral uniaxial stretching can be performed using a tenter type stretching machine.
- the fixing process in a fixing process is mainly performed in order to strengthen adsorption
- the fixing treatment can be performed by immersing the stretched PVA film in a fixing treatment bath.
- an aqueous solution containing one or more of boron compounds such as boric acid such as boric acid and borax can be used.
- the concentration of the boron compound in the aqueous solution containing the boron compound used as the fixing treatment bath is generally preferably in the range of 2 to 15% by mass, and more preferably in the range of 3 to 10% by mass.
- the temperature of the fixing treatment bath is preferably in the range of 15 to 60 ° C, more preferably in the range of 25 to 40 ° C.
- At least one process selected from the group consisting of a swelling process, a dyeing process, and a crosslinking process is used as a water contact process, and both ends in the width direction of the PVA film in which water adheres to the surface after passing through the water contact process
- a gas may be sprayed on the surface.
- each of the swelling process, the dyeing process, the crosslinking process, the stretching process, and the fixing process process has a water contact process in this order, and at least the swelling process, the dyeing process, and the crosslinking process are passed.
- the aspect which sprays gas to the width direction both ends of the PVA film which water adhered to the back surface is mentioned, and as a more preferred mode of the present invention, a swelling process, a dyeing process, a crosslinking process, an extending process, and a fixing process process, All have this order as a water contact process, and the aspect which sprays gas on the width direction both ends of the PVA film in which water adhered to the surface after passing through at least a swelling process, a dyeing process, a crosslinking process, and a fixing treatment process among these.
- a swelling process a dyeing process, a crosslinking process, and a fixing treatment process
- gas to be blown there are no particular limitations on the type of gas to be blown, and examples thereof include nitrogen gas, argon gas, air, and the like, but air is preferable because it is inexpensive.
- the wind speed of the gas to blow Since generation
- the upper limit of the wind speed is not particularly limited. However, if the wind speed is too high, the PVA film tends to be wrinkled. Therefore, the wind speed is preferably 20 m / second or less.
- Step of contacting the thin body The contact of the thin body in the step of bringing the thin body into contact with both ends in the width direction of the PVA film having water attached to the surface, which is caused by passing the water contact step, may be performed after the stretching step. Although it becomes possible to reduce the occurrence of film breakage due to shrinkage in the drying process, the film breakage during the production of the polarizing film is particularly likely to occur during stretching. It is preferable to have a step of contacting.
- At least one process selected from the group consisting of a swelling process, a dyeing process, and a crosslinking process is used as a water contact process, and both ends in the width direction of the PVA film in which water adheres to the surface after passing through the water contact process What is necessary is just to make a thin body contact.
- the thin body is formed at both ends in the width direction of the PVA film in which water adheres to the surface after passing through the water contact step. Or, for some of these water contact processes, the thin body is contacted to both ends in the width direction of the PVA film with water adhering to the surface after passing through the water contact process. Can be either.
- each of the swelling step, the dyeing step, the crosslinking step and the stretching step has a water contact step in this order, and at least the surface after passing through the swelling step, the dyeing step and the crosslinking step. The aspect which makes a thin body contact the width direction both ends of the PVA film to which water adhered is mentioned.
- the material constituting the thin body is not particularly limited, and examples thereof include plastics; fabrics such as woven fabrics, knitted fabrics and nonwoven fabrics; composites obtained by impregnating these fabrics with plastics and the like; metals; glass and the like.
- the said thin body is a plastic film.
- plastic constituting the plastic film examples include various thermoplastic resins such as polyolefin (polyethylene, polypropylene, polymethylpentene, etc.), polystyrene, polycarbonate, polyvinyl chloride, methacrylic resin, nylon, polyester (polyethylene terephthalate, etc.), And copolymers having a plurality of types of monomer units constituting these thermoplastic resins.
- polyolefin polyethylene, polypropylene, polymethylpentene, etc.
- polystyrene polycarbonate
- copolymers having a plurality of types of monomer units constituting these thermoplastic resins In the plastic film, only one type of plastic or two or more types of plastic may be included. Among these, since generation
- the water contact angle of the thin body in the portion in contact with the PVA film is 90 ° or less.
- the water contact angle is more preferably 80 ° or less, and further preferably 60 ° or less.
- the water contact angle can be measured by a contact angle test as described in JIS R3257: 1999, and can be specifically measured by the method described later in the examples.
- the water contact angle can be adjusted, for example, by corona treatment of the surface of the thin body using a corona surface treatment apparatus (Kasuga Denki Co., Ltd.).
- the said thickness is preferably 10 micrometers or more, 15 micrometers or more It is more preferable that it is 20 ⁇ m or more.
- the said thickness can be made into 1 cm or less, but since the polarizing film can be manufactured more smoothly, the said thickness may be 5 mm or less. Preferably, it is 1 mm or less, more preferably 500 ⁇ m or less, and particularly preferably 100 ⁇ m or less.
- variety (when making it contact with a PVA film)
- the length in the same direction as the width direction of the PVA film is preferably 1 cm or more, more preferably 2 cm or more, still more preferably 3 cm or more, and particularly preferably 5 cm or more.
- variety is 20 cm or less from a viewpoint of reducing disturbances, such as a damage
- the width of the portion where the PVA film and the thin body are in contact preferably 0.5 cm or more, More preferably 1 cm or more, still more preferably 1.5 cm or more, particularly preferably 2 cm or more, and preferably 20 cm or less, more preferably 10 cm or less.
- both ends of the PVA film in the width direction with water attached to the surface after the PVA film immersed in water by the water immersion step is taken out of the water. It is sufficient that the thin body is brought into contact with the PVA film, for example, the position before the thin body is brought into contact with both ends of the PVA film in the width direction before the PVA film immersed in water by the water immersion step is taken out of the water. Or you may set to the time of taking out from water, or you may set the said position to the time after taking out the PVA film immersed in water by the water immersion process from water.
- the thin body may contact the both ends of the width direction of the PVA film only once, it may be performed twice or more.
- the production method of the present invention has a water immersion step as the water contact step, it is possible to more effectively suppress the occurrence of folding at the end in the width direction of the PVA film. It is preferable to set the position at which the thin body starts to come into contact with both ends in the width direction of the film at a time point before or after taking out the PVA film immersed in water by the water dipping process. In this case, both ends of the PVA film in the width direction are in contact with the thin body in the portion where the PVA film is separated from the water surface.
- Method A For the moving direction of the PVA film, by installing a pair of thin bodies with the upstream end as a fixed end and the downstream end as a free end in the vicinity of both ends of the PVA film , A method of contacting the PVA film over the downstream end from any position between the upstream end and the downstream end by the tension or water pressure by the water, Method B: A pair of endless belt-like thin bodies are installed in the vicinity of both ends of the PVA film, and the portions that are brought into contact with both ends in the width direction of the PVA film are along the moving direction of the PVA film as necessary.
- the method A is preferable because the operation is simple.
- FIG. 1 is a schematic view showing a contact method according to Method A, (a) is a view seen from the upper side in the vertical direction, and (b) is a view seen from the side.
- FIG. 1 shows that when a PVA film 1 is moving in the length direction, a pair of thin plastic films 2 installed in the vicinity of both ends of the PVA film are seen from the lower side in the vertical direction of the PVA film 1. A mode of contacting the PVA film 1 is shown.
- the plastic film 2 has an upstream end 3 in the moving direction of the PVA film as a fixed end, and a downstream end 4 in the free end. Then, from the position 5 between the fixed end 3 and the free end 4 on the plastic film 2 to the free end 4, the end 6 in the width direction of the PVA film and the plastic film are in contact.
- FIG. 2 is a schematic view showing a contact method according to Method B, (a) is a view seen from the upper side in the vertical direction, and (b) is a view seen from the side.
- FIG. 2 shows that when the PVA film 1 is moving in the length direction, a pair of endless belt-like plastic films 2 installed in the vicinity of both ends of the PVA film are perpendicular to the PVA film 1. The mode which contacts the PVA film 1 from the direction lower side is shown.
- the endless belt-shaped plastic film 2 is moving at a speed substantially equal to the moving speed of the PVA film so that the portions brought into contact with both ends in the width direction of the PVA film are along the moving direction of the PVA film.
- a polarizing film from a PVA film after passing through the water contact step, preferably after taking out the PVA film immersed in water by the water immersion step (in one example, the next water contact step).
- the PVA film is held or conveyed using one or two or more rolls (guide roll, nip roll, etc.). In the production method of the present invention, it is preferable to use such a roll.
- both ends of the PVA film in the width direction are between the PVA film and the first contact roll after leaving the water surface. It is preferable to bring a thin body into contact with the part.
- a PVA film (both surfaces) is from a water surface.
- the length in the length direction of the PVA film at the portion where the thin body is in contact with both ends in the width direction with respect to the length L1 in the length direction of the PVA film between the roll and the first contact after the separation The ratio of L2 (100 ⁇ L2 / L1 (%)) is preferably 10% or more because it can more effectively suppress the occurrence of folding at the end in the width direction of the PVA film. % Or more is more preferable, and 80% or more is still more preferable.
- the said ratio can be 95% or less.
- FIG. 3 shows a case in which a thin plastic film 2 is brought into contact with both ends in the width direction of the PVA film 1 between the PVA film 1 and the first roll 10 after the PVA film 1 leaves the water surface.
- the position of L1 and L2 in the case of making the plastic film 2 contact is shown schematically.
- the position 5 at which the plastic film 2 starts to come into contact with both ends in the width direction of the PVA film 1 is set to a time point before the PVA film 1 immersed in water by the water immersion process is taken out from the water. That is, both ends of the PVA film 1 in the width direction are already in contact with the plastic film 2 in the portion where the PVA film 1 is separated from the water surface 8. Therefore, in FIG. 3, the starting point of L1 and the starting point of L2 are the same.
- the PVA film which water adhered to the surface produced by letting a water contact process pass etc.
- the PVA film which water adhered to the surface after taking out the PVA film immersed in water by the water immersion process from water Between two successive rolls of at least one set of these rolls (until the PVA film leaves the upstream roll and contacts the downstream roll) it is also preferable to bring the thin body into contact with both ends of the PVA film in the width direction because the occurrence of folding at the ends of the PVA film in the width direction can be more effectively suppressed.
- the thin body is contacted at both ends in the width direction of the PVA film with water attached to the surface after the PVA film is separated from the water surface until the first contact with the roll. Then, after releasing the contact with the thin body, between the two continuous rolls of at least one of the two or more rolls sequentially contacted by the PVA film having water attached to the surface, again The method of making a thin body contact the both ends of the width direction of a PVA film is mentioned.
- the PVA film which the water adhered to the surface contacts has two or more rolls which the PVA film which the water adhered to the surface contacts sequentially, and between two rolls of at least 1 set of these rolls, a PVA film of When the thin body is brought into contact with both ends in the width direction, the portion where the thin body is in contact with both ends in the width direction with respect to the length L3 in the length direction of the PVA film between the two continuous rolls.
- the ratio (100 ⁇ L4 / L3 (%)) of the length L4 in the length direction of the PVA film can more effectively suppress the occurrence of folding at the end in the width direction of the PVA film, 10 % Or more, preferably 30% or more, and more preferably 80% or more.
- the said ratio can be 95% or less.
- FIG. 4 shows a case where the plastic film 2 as a thin body is brought into contact with both ends in the width direction of the PVA film 1 between a pair of two continuous rolls 11, and the plastic film 2 is brought into contact with the method A.
- a polarizing film can be produced by stretching, further performing a fixing treatment as required, and then drying.
- the drying conditions are not particularly limited, but the drying temperature is preferably within the range of 30 to 150 ° C, and more preferably within the range of 50 to 130 ° C.
- a polarizing film excellent in dimensional stability is easily obtained by drying at a temperature within the above range.
- the polarizing film obtained as described above is usually used as a polarizing plate by attaching a protective film that is optically transparent and has mechanical strength to both sides or one side.
- a protective film a cellulose triacetate (TAC) film, an acetic acid / cellulose butyrate (CAB) film, an acrylic film, a polyester film, or the like can be used.
- TAC cellulose triacetate
- CAB acetic acid / cellulose butyrate
- acrylic film a polyester film, or the like
- polyester film or the like
- the adhesive for bonding include PVA adhesives and urethane adhesives, among which PVA adhesives are suitable.
- Water contact angle of plastic film A 200 mm ⁇ 15 mm strip-shaped film piece is cut out from the same plastic film as the plastic film used in the following Examples or Comparative Examples, and the water contact angle on the surface of the film piece in contact with the PVA film is determined according to JIS R3257: 1999. It measured based on the description of (the wettability test method of the substrate glass surface). That is, a water droplet of 4 ⁇ l or less is allowed to stand on a horizontally placed film piece, from the shape of the water drop to the radius r (mm) of the surface of the water drop in contact with the film piece, and from the film piece surface to the top of the water drop.
- the total draw ratio is increased stepwise by 0.1 by adjusting the draw ratio in the drawing step, and set immediately before the total draw ratio when the film breaks.
- the total draw ratio was set as the draw ratio at which continuous operation was possible.
- Example 1 A long PVA film having a thickness of 20 ⁇ m and a width of 1 m (including PVA, glycerin and a surfactant, the glycerin content is 12 parts by mass with respect to 100 parts by mass of PVA, and the surfactant content is 100 parts by mass of PVA)
- the PVA film is 0.03 parts by mass with respect to the saponification product of PVA, which is a homopolymer of vinyl acetate, the polymerization degree of PVA is 2,400, and the saponification degree of PVA is 99.9 mol%.
- the film roll was continuously unwound and subjected to the swelling process, the dyeing process and the crosslinking process in this order.
- the PVA film was immersed in distilled water (temperature: 30 ° C.) for 1 minute, and uniaxially stretched in the length direction at a stretching ratio of 2.0 times. Further, as a dyeing process, the PVA film is in an aqueous solution containing iodine pigments (concentration of iodine used: 0.05 mass%, concentration of potassium iodide used: 1.2 mass%, temperature: 30 ° C.). And uniaxially stretched in the length direction at a stretch ratio of 1.2.
- the PVA film was immersed in an aqueous boric acid solution (boric acid concentration: 2.6% by mass, temperature: 30 ° C.) for 2 minutes, and uniaxially stretched at a draw ratio of 1.1 times in the length direction. .
- the width direction both ends of the PVA film in the state where water adhered to the surface after taking out the PVA film immersed in water by these each process from water Then, air was blown at a wind speed of 2.0 m / sec so as to be substantially along the PVA film surface from the width direction center side of the PVA film toward the width direction outer side. The air was blown using an air blowing nozzle.
- the stretching step was continuously performed following the above-described crosslinking step, and a polarizing film was produced through a fixing treatment step and a drying step in this order.
- the PVA film is uniaxially stretched in a length direction in a boric acid aqueous solution (boric acid concentration: 2.8 mass%, potassium iodide concentration: 5 mass%, temperature: 57 ° C.) at a stretching ratio of 1.9 times. (The total draw ratio including the draw ratio of the pre-stretch is 5.0 times).
- the fixing treatment step was performed by immersing the stretched PVA film in an aqueous boric acid solution (boric acid concentration: 2.6 mass%, potassium iodide concentration: 5 mass%, temperature: 22 ° C.) for 2 minutes. . Furthermore, the drying process was performed by drying the stretched PVA film at 60 ° C. for 1 minute. In addition, the width direction outer side from the width direction center part side of the PVA film in the width direction both ends of the PVA film in a state where water has adhered to the surface after taking out the PVA film immersed in water by the fixing treatment step Then, air was blown at a wind speed of 2.0 m / sec so as to substantially follow the PVA film surface. The air was blown using an air blowing nozzle.
- Example 2 A polarizing film was continuously produced in the same manner as in Example 1 except that the thickness of the PVA film was changed to 15 ⁇ m (Example 2) or 60 ⁇ m (Example 3).
- Example 4 In any of the swelling process, the dyeing process, the crosslinking process, and the fixing treatment process, it was continuously performed in the same manner as in Example 1 except that the air speed of air blown to both ends in the width direction of the PVA film was 1.0 m / second. A polarizing film was manufactured.
- Example 5 About the fixing process, the polarizing film was continuously manufactured like Example 1 except not having sprayed air.
- Example 6 About the swelling process, the bridge
- Example 1 A polarizing film was continuously produced in the same manner as in Example 1 except that air was not blown in any of the swelling process, the dyeing process, the crosslinking process, and the fixing process.
- Example 7 A long PVA film having a thickness of 30 ⁇ m and a width of 1 m (including PVA, glycerin and a surfactant, the glycerin content being 12 parts by mass with respect to 100 parts by mass of PVA, and the surfactant content being 100 parts by mass of PVA)
- the PVA film is 0.03 parts by mass with respect to the saponification product of PVA, which is a homopolymer of vinyl acetate, the polymerization degree of PVA is 2,400, and the saponification degree of PVA is 99.9 mol%.
- the film roll was continuously unwound and subjected to the swelling process, the dyeing process and the crosslinking process in this order.
- the PVA film was immersed in distilled water (temperature: 30 ° C.) for 1 minute, and uniaxially stretched in the length direction at a stretching ratio of 2.0 times. Further, as a dyeing process, the PVA film is in an aqueous solution containing iodine pigments (concentration of iodine used: 0.05 mass%, concentration of potassium iodide used: 1.2 mass%, temperature: 30 ° C.). And uniaxially stretched in the length direction at a stretch ratio of 1.2.
- the PVA film was immersed in an aqueous boric acid solution (boric acid concentration: 2.6% by mass, temperature: 30 ° C.) for 2 minutes, and uniaxially stretched at a draw ratio of 1.1 times in the length direction. .
- any of the swelling process, the dyeing process, and the crosslinking process PVA in a state where water adheres to the surface after the PVA film immersed in water by these processes is taken out from the water.
- the film was brought into contact with the guide roll, and then further brought into contact with a pair of nip rolls.
- the plastic film is brought into contact with both ends in the width direction of the PVA film, and also between the guide roll and the nip roll.
- the plastic film was brought into contact with both ends in the width direction of the PVA film with water attached to the surface.
- Each of the plastic films used is a biaxially stretched polyethylene terephthalate (PET) film ("Lumirror” S10 manufactured by Toray Industries, Inc.) having a thickness of 75 ⁇ m and a width of 3 cm, and the surface on the side in contact with the PVA film by corona treatment The water contact angle of the PVA film is adjusted to 57 °. With respect to the direction of movement of the PVA film, the upstream end of the plastic film is the fixed end and the downstream end is the free end. The plastic film was brought into contact with both end portions in the width direction of the PVA film by installing on the lower side (the width of the contact portion at each end portion was 2 cm).
- PET polyethylene terephthalate
- the position at which the plastic film is brought into contact with both ends in the width direction of the PVA film is set to the time point before the PVA film immersed in water is taken out of the water in each process. By doing this, the width direction both ends of the PVA film were made to contact the plastic film in the part which the PVA film leaves
- 100 ⁇ L2 / L1 was set to 80%
- 100 ⁇ L4 / L3 was set to 80%.
- the stretching step was continuously performed following the above-described crosslinking step, and a polarizing film was produced through a fixing treatment step and a drying step in this order.
- the PVA film is uniaxially stretched in a length direction in a boric acid aqueous solution (boric acid concentration: 2.8 mass%, potassium iodide concentration: 5 mass%, temperature: 57 ° C.) at a stretching ratio of 1.9 times. (The total draw ratio including the draw ratio of the pre-stretch is 5.0 times).
- the fixing treatment step was performed by immersing the stretched PVA film in an aqueous boric acid solution (boric acid concentration: 2.6 mass%, potassium iodide concentration: 5 mass%, temperature: 22 ° C.) for 2 minutes. . Furthermore, the drying process was performed by drying the stretched PVA film at 60 ° C. for 1 minute.
- Example 8 A polarizing film was continuously produced in the same manner as in Example 7 except that the thickness of the PVA film was changed to 15 ⁇ m (Example 8) or 60 ⁇ m (Example 9).
- Example 10 In any of the swelling process, the dyeing process and the crosslinking process, the polarizing film was continuously formed in the same manner as in Example 7 except that 100 ⁇ L2 / L1 was set to 5% and 100 ⁇ L4 / L3 was set to 5%. Manufactured.
- Example 11 A polarizing film was continuously produced in the same manner as in Example 7 except that the plastic film was not brought into contact with the crosslinking step.
- Example 12 Regarding the contact of the plastic film, a polarizing film was continuously produced in the same manner as in Example 7 except that the width of the contact portion at each end was 1 cm.
- Example 13 All of the plastic films used are polyethylene terephthalate (PET) films with a thickness of 75 ⁇ m and a width of 3 cm, and the water contact angle on the surface in contact with the PVA film is adjusted to 100 ° by corona treatment. A polarizing film was continuously produced in the same manner as in Example 7 except that was used.
- PET polyethylene terephthalate
- Each of the plastic films used is a linear low density polyethylene (LLDPE) film (SE620N Tamapoly Co., Ltd.) having a thickness of 50 ⁇ m and a width of 3 cm, and water on the surface in contact with the PVA film by corona treatment.
- a polarizing film was continuously produced in the same manner as in Example 7 except that a contact angle adjusted to 85 ° was used.
- Example 2 A polarizing film was continuously produced in the same manner as in Example 7 except that the plastic film was not contacted in any of the swelling process, the dyeing process, and the crosslinking process.
- Example 3 A polarizing film was continuously produced in the same manner as in Example 8 except that the plastic film was not contacted in any of the swelling process, the dyeing process, and the crosslinking process.
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Abstract
Description
(i)コート作業やその後の乾燥作業が煩雑である。
(ii)PVA層の不溶化処理のための熱処理を積層体の状態で行う必要があるため、使用されるプラスチックフィルムが熱処理後も延伸可能なものに限定され、コスト高になる。
(iii)プラスチックフィルム上にコート法によってPVA層を形成してなる積層体では、プラスチックフィルムとPVA層との間の接着強度が比較的高く、このような接着強度の高い積層体を延伸すると、PVA層の適度なネックインが妨げられて、偏光性能に優れる偏光フィルムが得られにくい。
[1]PVAフィルムを延伸する延伸工程を有する偏光フィルムの製造方法であって、表面に水が付着したPVAフィルムの幅方向両端部に気体を吹き付けるおよび/または薄状体を接触させる工程を有する、製造方法;
[2]PVAフィルムを水に浸漬する水浸漬工程を有し、表面に水が付着したPVAフィルムが、水浸漬工程によって水に浸漬されたPVAフィルムを水から取り出した後のものである、上記[1]の製造方法;
[3]水浸漬工程が、膨潤工程、染色工程、架橋工程、延伸工程および固定処理工程からなる群より選ばれる少なくとも1つである、上記[2]の製造方法;
[4]表面に水が付着したPVAフィルムの幅方向両端部に薄状体を接触させる工程を有する製造方法であって、水浸漬工程によって水に浸漬されたPVAフィルムを水から取り出した後にPVAフィルムが接触する1個以上のロールを有し、PVAフィルムが水面から離れた後より最初に接触するロールまでの間において、PVAフィルムの幅方向両端部に薄状体を接触させる、上記[2]または[3]の製造方法;
[5]PVAフィルムが水面から離れた後より最初に接触するロールまでの間における、PVAフィルムの長さ方向の長さに対する、幅方向両端部に薄状体が接触している部分のPVAフィルムの長さ方向の長さの割合が10%以上である、上記[4]の製造方法;
[6]表面に水が付着したPVAフィルムの幅方向両端部に薄状体を接触させる工程を有する製造方法であって、PVAフィルムが水面から離れる部分において、PVAフィルムの幅方向両端部が薄状体と接触している、上記[2]~[5]のいずれか1つの製造方法;
[7]表面に水が付着したPVAフィルムの幅方向両端部に薄状体を接触させる工程を有する製造方法であって、表面に水が付着したPVAフィルムが順次接触する2個以上のロールを有し、これらのうちの少なくとも1組の連続する2個のロール間において、PVAフィルムの幅方向両端部に薄状体を接触させる、上記[1]~[6]のいずれか1つの製造方法;
[8]上記連続する2個のロール間における、PVAフィルムの長さ方向の長さに対する、幅方向両端部に薄状体が接触している部分のPVAフィルムの長さ方向の長さの割合が10%以上である、上記[7]の製造方法;
[9]表面に水が付着したPVAフィルムの幅方向両端部に薄状体を接触させる工程を有する製造方法であって、薄状体の幅が1cm以上である、上記[1]~[8]のいずれか1つの製造方法;
[10]表面に水が付着したPVAフィルムの幅方向両端部に薄状体を接触させる工程を有する製造方法であって、PVAフィルムと接触する部分における薄状体の水接触角が90°以下である、上記[1]~[9]のいずれか1つの製造方法;
[11]表面に水が付着したPVAフィルムの幅方向両端部に風速が0.1m/秒以上の気体を吹き付ける、上記[1]~[10]のいずれか1つの製造方法;
[12]表面に水が付着したPVAフィルムの幅方向両端部にプラスチックフィルムを接触させる工程を有する、上記[1]~[11]のいずれか1つの製造方法;
[13]延伸工程の前に、表面に水が付着したPVAフィルムの幅方向両端部に気体を吹き付けるおよび/または薄状体を接触させる工程を有する、上記[1]~[12]のいずれか1つの製造方法;
[14]PVAフィルムの厚みが50μm以下である、上記[1]~[13]のいずれか1つの製造方法;
に関する。
偏光フィルムを製造するための本発明の製造方法は、PVAフィルムを延伸する延伸工程を有する。そして本発明の製造方法では、膨潤工程、染色工程、架橋工程、延伸工程、固定処理工程等のPVAフィルムを水と接触させる水接触工程を通過させるなどして生じた、表面に水が付着したPVAフィルムの幅方向両端部に対して、気体を吹き付ける工程および/または薄状体を接触させる工程を有する。通常、PVAフィルムを用いて偏光フィルムを製造する場合には、水接触工程を通過した後にPVAフィルムの幅方向の端部に折れ込みが発生しやすく、それが原因となって、延伸工程における延伸切れや乾燥工程における収縮によるフィルムの破断などが発生しやすくなるが、上記のように、表面に水が付着した状態のPVAフィルムの幅方向両端部に気体を吹き付けたり、薄状体を接触させたりすることにより、当該PVAフィルムの幅方向の端部における折れ込みの発生が抑制されて延伸時や乾燥時などにおけるフィルムの破断の発生が低減され、また、より高い延伸倍率で延伸することができて偏光性能に優れた偏光フィルムが容易に製造されるものと考えられる。
PVAフィルムを構成するPVAとしては、酢酸ビニル、ギ酸ビニル、プロピオン酸ビニル、酪酸ビニル、ピバリン酸ビニル、バーサティック酸ビニル、ラウリン酸ビニル、ステアリン酸ビニル、安息香酸ビニル、酢酸イソプロペニル等のビニルエステルの1種または2種以上を重合して得られるポリビニルエステルをけん化することにより得られるものを使用することができる。上記のビニルエステルの中でも、PVAの製造の容易性、入手の容易性、コスト等の点から、分子中にビニルオキシカルボニル基(H2C=CH-O-CO-)を有する化合物が好ましく、酢酸ビニルがより好ましい。
これらの界面活性剤は1種を単独でまたは2種以上を組み合わせて使用することができる。
本発明の製造方法では、PVAフィルムを水と接触させる水接触工程を通過させるなどして生じた、表面に水が付着したPVAフィルムの幅方向両端部に気体を吹き付けるおよび/または薄状体を接触させる工程を有する。偏光フィルムは、通常、膨潤工程、染色工程、架橋工程、延伸工程、固定処理工程などの各工程を経て製造することができ、本発明の製造方法は、これらの工程のうちの1つまたは2つ以上を水接触工程として有することができる。
水接触工程において使用される水は純水に限定されず、各工程の目的に応じて、後述するような水溶液や更には水性分散液などを用いることもできる。
以下に、水接触工程として採用することのできる工程も含め、本発明の製造方法において採用することのできる各工程をより詳細に説明する。
膨潤工程における膨潤処理は、PVAフィルムを水に浸漬することにより行うことができる。水に浸漬する際の水の温度としては、20~40℃の範囲内であることが好ましく、22~38℃の範囲内であることがより好ましく、25~35℃の範囲内であることが更に好ましい。また、水に浸漬する時間としては、例えば、0.5~5分間の範囲内であることが好ましく、1~3分間の範囲内であることがより好ましい。なお、水に浸漬する際の水は純水に限定されず、各種成分が溶解した水溶液であってもよいし、水と水性媒体との混合物であってもよい。
染色工程における染色処理は、PVAフィルムを二色性色素を含む水溶液中に浸漬することにより行うことができる。二色性色素を含む水溶液中における二色性色素の濃度は使用される二色性色素の種類などに応じて適宜設定することができ、例えば0.001~1質量%の範囲内とすることができるが、二色性色素を含む水溶液としてヨウ素-ヨウ化カリウム水溶液を用いる場合には、ヨウ素系色素を効率良くPVAフィルムに吸着させることができることから、使用されるヨウ素(I2)の濃度として0.01~1.0質量%の範囲内であることが好ましく、使用されるヨウ化カリウム(KI)の濃度として0.01~10質量%の範囲内であることが好ましい。二色性色素を含む水溶液の温度は、二色性色素を効率良くPVAフィルムに吸着させることができることから、20~50℃の範囲内であることが好ましく、25~40℃の範囲内であることがより好ましい。なお、二色性色素を予め含有させたPVAフィルムを用いる場合には、染色工程を省略することができる。
架橋工程を行うと、PVAフィルムに架橋が導入され、比較的高い温度かつ湿式で延伸工程を行う際にPVAが水へ溶出するのを効果的に防止することができる。このような観点などから、架橋工程は染色工程の後に行うのが好ましい。架橋処理は、PVAフィルムを架橋剤を含む水溶液中に浸漬することにより行うことができる。当該架橋剤としては、ホウ酸、ホウ砂等のホウ酸塩などのホウ素化合物の1種または2種以上を使用することができる。架橋剤を含む水溶液における架橋剤の濃度は1~15質量%の範囲内であることが好ましく、2~7質量%の範囲内であることがより好ましい。架橋剤を含む水溶液はヨウ化カリウム等の助剤を含有してもよい。架橋剤を含む水溶液の温度は、20~50℃の範囲内であることが好ましく、25~40℃の範囲内であることがより好ましい。
PVAフィルムを延伸する延伸工程において、その延伸方法に特に制限はなく、湿式延伸法および乾式延伸法のうちのいずれで行ってもよい。湿式延伸法の場合は、ホウ酸、ホウ砂等のホウ酸塩などのホウ素化合物の1種または2種以上を含む水溶液中で行うこともできるし、上記した二色性色素を含む水溶液中や後述する固定処理浴中で行うこともできる。また乾式延伸法の場合は、室温のまま延伸を行ってもよいし、熱をかけながら延伸してもよいし、吸水後に延伸してもよい。これらの中でも、得られる偏光フィルムにおける幅方向の厚みの均一性の点から湿式延伸法が好ましく、ホウ酸水溶液中で延伸することがより好ましい。ホウ酸水溶液中におけるホウ酸の濃度は0.5~6.0質量%の範囲内であることが好ましく、1.0~5.0質量%の範囲内であることがより好ましく、1.5~4.0質量%の範囲内であることが更に好ましい。上記したホウ素化合物を含む水溶液はヨウ化カリウムを含有してもよく、その濃度は0.01~10質量%の範囲内であることが好ましい。
固定処理工程における固定処理は、主として、延伸されたPVAフィルムへの二色性色素の吸着を強固にするために施される。固定処理は延伸されたPVAフィルムを固定処理浴中に浸漬することにより行うことができる。固定処理浴としては、ホウ酸、ホウ砂等のホウ酸塩などのホウ素化合物の1種または2種以上を含む水溶液を使用することができる。また、必要に応じて、固定処理浴中にヨウ素化合物や金属化合物を添加してもよい。固定処理浴として使用されるホウ素化合物を含む水溶液中におけるホウ素化合物の濃度は、一般に2~15質量%の範囲内であることが好ましく、3~10質量%の範囲内であることがより好ましい。固定処理浴の温度は、15~60℃の範囲内であることが好ましく、25~40℃の範囲内であることがより好ましい。
上記の水接触工程を通過させるなどして生じた、表面に水が付着したPVAフィルムの幅方向両端部に気体を吹き付ける工程における気体の吹き付けは、延伸工程の後に行っても乾燥工程における収縮によるフィルムの破断の発生を低減することが可能となるが、偏光フィルムを製造する際のフィルムの破断は延伸時に特に発生しやすいことから、延伸工程の前に、当該気体を吹き付ける工程を有することが好ましい。この場合において、膨潤工程、染色工程および架橋工程からなる群より選ばれる少なくとも1つの工程を水接触工程とし、当該水接触工程を通過した後の表面に水が付着したPVAフィルムの幅方向両端部に気体を吹き付ければよい。なお、当該気体を吹き付ける工程を複数有する場合は、そのうちの少なくとも1つの工程が延伸工程の前にあるのが好ましい。
上記の水接触工程を通過させるなどして生じた、表面に水が付着したPVAフィルムの幅方向両端部に薄状体を接触させる工程における薄状体の接触は、延伸工程の後に行っても乾燥工程における収縮によるフィルムの破断の発生を低減することが可能となるが、偏光フィルムを製造する際のフィルムの破断は延伸時に特に発生しやすいことから、延伸工程の前に、当該薄状体を接触させる工程を有することが好ましい。この場合において、膨潤工程、染色工程および架橋工程からなる群より選ばれる少なくとも1つの工程を水接触工程とし、当該水接触工程を通過した後の表面に水が付着したPVAフィルムの幅方向両端部に薄状体を接触させればよい。なお、当該薄状体を接触させる工程を複数有する場合は、そのうちの少なくとも1つの工程が延伸工程の前にあるのが好ましい。
方法A:PVAフィルムの移動方向について、その上流側の端部を固定端としその下流側の端部を自由端とした一対の薄状体を、PVAフィルムの両端部の近傍に設置することにより、水による張力や水圧などによって、当該薄状体の上流側の端部および下流側の端部の間のいずれかの位置より下流側の端部にかけて、PVAフィルムと接触させる方法、
方法B:一対のエンドレスベルト状の薄状体を、PVAフィルムの両端部の近傍に設置し、必要に応じてPVAフィルムの幅方向両端部に接触させる部分がPVAフィルムの移動方向に沿うように移動させながら、PVAフィルムと接触させる方法、
などが挙げられ、操作が簡便であることなどから方法Aが好ましい。なお、PVAフィルムの幅方向両端部に薄状体を接触させる際における方向に特に制限はなく、PVAフィルムの鉛直方向上側から接触させても、PVAフィルムの鉛直方向下側から接触させてもどちらでもよい。
延伸を行い、必要に応じて更に固定処理を行った後、乾燥することにより偏光フィルムを製造することができる。乾燥条件は特に制限されないが、乾燥温度は30~150℃の範囲内であることが好ましく、50~130℃の範囲内であることがより好ましい。上記範囲内の温度で乾燥することで寸法安定性に優れる偏光フィルムが得られやすい。
以上のようにして得られた偏光フィルムは、通常、その両面または片面に、光学的に透明で、かつ機械的強度を有する保護膜を貼り合わせて偏光板として使用される。保護膜としては、三酢酸セルロース(TAC)フィルム、酢酸・酪酸セルロース(CAB)フィルム、アクリル系フィルム、ポリエステル系フィルムなどを使用することができる。また、貼り合わせのための接着剤としては、PVA系接着剤やウレタン系接着剤などを挙げることができるが、中でもPVA系接着剤が好適である。
風速計を用いてJIS A1431:1994(空気調和・換気設備の風量測定方法)の記載に準拠して求めた。具体的には、以下の実施例または比較例において使用された気体(空気)吹き付け用ノズルより吹き付けられる気体の風速を求めた。当該測定は、温度:25℃、湿度:50%RHの条件下で行った。
以下の実施例または比較例において使用されたプラスチックフィルムと同じプラスチックフィルムから200mm×15mmの短冊状のフィルム片を切り出し、このフィルム片のPVAフィルムと接触する面における水接触角を、JIS R3257:1999(基板ガラス表面のぬれ性試験方法)の記載に準拠して測定した。すなわち、水平に置かれたフィルム片上に4μl以下の水滴を静置し、水滴の形状から、水滴のフィルム片に接している面の半径r(mm)、およびフィルム片表面から水滴の頂点までの高さh(mm)を測定し、下記式(1)により水接触角θ(°)を求めた。
θ = 2tan-1(h/r) (1)
なお、測定は5回実施し、その平均値をそのプラスチックフィルムの水接触角とした。また、測定は、温度:25℃、湿度:50%RHの条件下で行った。
以下の実施例または比較例において、延伸工程における延伸倍率を調整することにより全延伸倍率を0.1倍ずつ段階的に上げていき、フィルムの破断が発生したときの全延伸倍率の直前に設定した全延伸倍率を、連続運転可能な延伸倍率とした。
(a)透過率Tsの測定
以下の実施例または比較例で得られた偏光フィルムの幅方向の中央部から、偏光フィルムの長さ方向に2cm×幅方向に2cmの正方形のサンプルを2枚採取し、積分球付き分光光度計(日本分光株式会社製「V7100」)を用いて、JIS Z8722:2009(物体色の測定方法)に準拠し、C光源、2°視野の可視光領域の視感度補正を行い、1枚のサンプルについて、長さ方向に対して45°傾けた場合の光の透過率と-45°傾けた場合の光の透過率を測定して、それらの平均値Ts1(%)を求めた。もう1枚のサンプルについても同様にして、45°傾けた場合の光の透過率と-45°傾けた場合の光の透過率を測定して、それらの平均値Ts2(%)を求めた。下記式(2)によりTs1とTs2を平均し、偏光フィルムの透過率Ts(%)とした。
Ts = (Ts1+Ts2)/2 (2)
上記透過率Tsの測定で採取した2枚のサンプルを、その長さ方向が平行になるように重ねた場合の光の透過率T∥(%)、および、長さ方向が直交するように重ねた場合の光の透過率T⊥(%)を、上記「(a)透過率Tsの測定」の場合と同様にして測定し、下記式(3)により偏光度V(%)を求めた。
V = {(T∥-T⊥)/(T∥+T⊥)}1/2×100 (3)
以下の実施例または比較例で得られた偏光フィルムの幅方向中央部を通る線上で、長さ方向に間隔をあけて5箇所を設定し、各箇所のそれぞれについて、偏光フィルムの長さ方向に2cm×幅方向に2cmの正方形のサンプルを2枚採取し、上記と同様にして、透過率Ts(%)および偏光度V(%)を求めた。そして各実施例または比較例毎に、得られた5つの透過率Tsの最大値と最小値の差を変動幅(Ts)とし、また、得られた5つの偏光度Vの最大値と最小値の差を変動幅(V)とした。
厚みが20μmで幅が1mの長尺のPVAフィルム(PVAとグリセリンと界面活性剤を含み、グリセリンの含有量がPVA100質量部に対して12質量部で、界面活性剤の含有量がPVA100質量部に対して0.03質量部であるPVAフィルム。PVAは酢酸ビニルの単独重合体のけん化物であり、PVAの重合度は2,400で、PVAのけん化度は99.9モル%。)を、そのフィルムロールから連続的に巻き出し、膨潤工程、染色工程および架橋工程に、この順で連続的に供した。
PVAフィルムの厚みを、15μm(実施例2)または60μm(実施例3)に変更したこと以外は実施例1と同様にして、連続的に偏光フィルムを製造した。
膨潤工程、染色工程、架橋工程および固定処理工程のいずれについても、PVAフィルムの幅方向両端部に吹き付ける空気の風速を1.0m/秒としたこと以外は実施例1と同様にして、連続的に偏光フィルムを製造した。
固定処理工程については空気の吹き付けを行わなかったこと以外は実施例1と同様にして、連続的に偏光フィルムを製造した。
膨潤工程、架橋工程および固定処理工程については空気の吹き付けを行わなかったこと以外は実施例1と同様にして、連続的に偏光フィルムを製造した。
膨潤工程、染色工程、架橋工程および固定処理工程のいずれについても空気の吹き付けを行わなかったこと以外は実施例1と同様にして、連続的に偏光フィルムを製造した。
厚みが30μmで幅が1mの長尺のPVAフィルム(PVAとグリセリンと界面活性剤を含み、グリセリンの含有量がPVA100質量部に対して12質量部で、界面活性剤の含有量がPVA100質量部に対して0.03質量部であるPVAフィルム。PVAは酢酸ビニルの単独重合体のけん化物であり、PVAの重合度は2,400で、PVAのけん化度は99.9モル%。)を、そのフィルムロールから連続的に巻き出し、膨潤工程、染色工程および架橋工程に、この順で連続的に供した。
なお、膨潤工程、染色工程および架橋工程のいずれについても、PVAフィルムの幅方向両端部にプラスチックフィルムを接触させ始める位置を各工程によって水に浸漬されたPVAフィルムを水から取り出す前の時点に設定することによって、PVAフィルムが各工程における水の水面から離れる部分においてPVAフィルムの幅方向両端部がプラスチックフィルムと接触しているようにした。膨潤工程、染色工程および架橋工程のいずれについても、100×L2/L1を80%とし、100×L4/L3を80%とした。
PVAフィルムの厚みを、15μm(実施例8)または60μm(実施例9)に変更したこと以外は実施例7と同様にして、連続的に偏光フィルムを製造した。
膨潤工程、染色工程および架橋工程のいずれについても、100×L2/L1を5%とし、100×L4/L3を5%としたこと以外は実施例7と同様にして、連続的に偏光フィルムを製造した。
架橋工程についてはプラスチックフィルムを接触させなかったこと以外は実施例7と同様にして、連続的に偏光フィルムを製造した。
プラスチックフィルムの接触について、各端部における接触部分の幅をいずれも1cmとしたこと以外は実施例7と同様にして、連続的に偏光フィルムを製造した。
使用したプラスチックフィルムについて、いずれも、厚みが75μmで幅が3cmのポリエチレンテレフタレート(PET)フィルムであり、コロナ処理によってPVAフィルムと接触する側の面の水接触角が100°に調節されているものを用いたこと以外は実施例7と同様にして、連続的に偏光フィルムを製造した。
使用したプラスチックフィルムについて、いずれも、厚みが50μmで幅が3cmの直鎖状低密度ポリエチレン(LLDPE)フィルム(SE620N タマポリ株式会社製)であり、コロナ処理によってPVAフィルムと接触する側の面の水接触角が85°に調節されているものを用いたこと以外は実施例7と同様にして、連続的に偏光フィルムを製造した。
膨潤工程、染色工程および架橋工程のいずれについてもプラスチックフィルムを接触させなかったこと以外は実施例7と同様にして、連続的に偏光フィルムを製造した。
膨潤工程、染色工程および架橋工程のいずれについてもプラスチックフィルムを接触させなかったこと以外は実施例8と同様にして、連続的に偏光フィルムを製造した。
Claims (14)
- ポリビニルアルコールフィルムを延伸する延伸工程を有する偏光フィルムの製造方法であって、表面に水が付着したポリビニルアルコールフィルムの幅方向両端部に気体を吹き付けるおよび/または薄状体を接触させる工程を有する、製造方法。
- ポリビニルアルコールフィルムを水に浸漬する水浸漬工程を有し、表面に水が付着したポリビニルアルコールフィルムが、水浸漬工程によって水に浸漬されたポリビニルアルコールフィルムを水から取り出した後のものである、請求項1に記載の製造方法。
- 水浸漬工程が、膨潤工程、染色工程、架橋工程、延伸工程および固定処理工程からなる群より選ばれる少なくとも1つである、請求項2に記載の製造方法。
- 表面に水が付着したポリビニルアルコールフィルムの幅方向両端部に薄状体を接触させる工程を有する製造方法であって、水浸漬工程によって水に浸漬されたポリビニルアルコールフィルムを水から取り出した後にポリビニルアルコールフィルムが接触する1個以上のロールを有し、ポリビニルアルコールフィルムが水面から離れた後より最初に接触するロールまでの間において、ポリビニルアルコールフィルムの幅方向両端部に薄状体を接触させる、請求項2または3に記載の製造方法。
- ポリビニルアルコールフィルムが水面から離れた後より最初に接触するロールまでの間における、ポリビニルアルコールフィルムの長さ方向の長さに対する、幅方向両端部に薄状体が接触している部分のポリビニルアルコールフィルムの長さ方向の長さの割合が10%以上である、請求項4に記載の製造方法。
- 表面に水が付着したポリビニルアルコールフィルムの幅方向両端部に薄状体を接触させる工程を有する製造方法であって、ポリビニルアルコールフィルムが水面から離れる部分において、ポリビニルアルコールフィルムの幅方向両端部が薄状体と接触している、請求項2~5のいずれか1項に記載の製造方法。
- 表面に水が付着したポリビニルアルコールフィルムの幅方向両端部に薄状体を接触させる工程を有する製造方法であって、表面に水が付着したポリビニルアルコールフィルムが順次接触する2個以上のロールを有し、これらのうちの少なくとも1組の連続する2個のロール間において、ポリビニルアルコールフィルムの幅方向両端部に薄状体を接触させる、請求項1~6のいずれか1項に記載の製造方法。
- 上記連続する2個のロール間における、ポリビニルアルコールフィルムの長さ方向の長さに対する、幅方向両端部に薄状体が接触している部分のポリビニルアルコールフィルムの長さ方向の長さの割合が10%以上である、請求項7に記載の製造方法。
- 表面に水が付着したポリビニルアルコールフィルムの幅方向両端部に薄状体を接触させる工程を有する製造方法であって、薄状体の幅が1cm以上である、請求項1~8のいずれか1項に記載の製造方法。
- 表面に水が付着したポリビニルアルコールフィルムの幅方向両端部に薄状体を接触させる工程を有する製造方法であって、ポリビニルアルコールフィルムと接触する部分における薄状体の水接触角が90°以下である、請求項1~9のいずれか1項に記載の製造方法。
- 表面に水が付着したポリビニルアルコールフィルムの幅方向両端部に風速が0.1m/秒以上の気体を吹き付ける工程を有する、請求項1~10のいずれか1項に記載の製造方法。
- 表面に水が付着したポリビニルアルコールフィルムの幅方向両端部にプラスチックフィルムを接触させる工程を有する、請求項1~11のいずれか1項に記載の製造方法。
- 延伸工程の前に、表面に水が付着したポリビニルアルコールフィルムの幅方向両端部に気体を吹き付けるおよび/または薄状体を接触させる工程を有する、請求項1~12のいずれか1項に記載の製造方法。
- ポリビニルアルコールフィルムの厚みが50μm以下である、請求項1~13のいずれか1項に記載の製造方法。
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